Tracking down parasitic current draw, MFA?

VW Derf

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Since parking our car for more than two days is a rare thing thing, I've never kept that close of an eye on parasitic draws or noticed any problems. That is until last month when we were away for two weeks and ended up with a dead battery (3 volts) when we returned. :( :eek: :(

Anyways the past few days I finally started to look at this closer and following the procedure to check the mV drop on the fuses I've found the following draws when my 2010 Golf Wagon is in sleep/alarm mode:

Fuse 11 - 11 mA
Fuse 10 - 6 mA
Fuse 8 - 133 mA (0.6mV on a 15Amp fuse).

From what I can tell fuse 8 is the "Multifunction display control module". Does anyone know if that is fuse 8 is indeed the MFA and what the consumption should be? I'm assuming it is too high as from what I've read total consumption over 60mA is a not great and 100mA is a concern.

Electrical wise I'm pretty stock except for a Polar FIS and a trailer light module that is spliced in.

VCDS just reports two errors on the radio (RCD510 -01303 and 02635) and the CAN Gateway "01303 - Telephone transceiver. Not sure about that, but it's been there for ever.

There were however a bunch of other errors from when the body shop replaced the sunroof that shattered due to road debris, but after clearing that I haven't seen it come back yet.

I'll have to get the battery tested/replaced as when the car is running it rarely gets over 13.1V-13.4V and when the engine is off it sits around 12.2-12.6 since that drain. When starting it sometimes dips down to about 10v for second.

Any thoughts on what to do next to find out what caused this draw or if I should be concerned?

Thanks
 

KERMA

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I wouldn't be concerned if it were me.
Batteries wear out just like anything else in a car. Probably almost due for replacement anyway.

The radio and telephone codes are very common. There's probably some "fix" that involves recoding the affected modules but otherwise those DTC are inconsequential.

But if you want to, just for giggles: before shutting off the car, try turning off the PolarFis by switching away from the phone screen. See if that affects the amp draw at all. Also could try removing the polar module completely if you feel curious in the name of science.

But I wouldn't be concerned at all.
 

740GLE

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BTW you give current draw, what were you seeing for voltage drops across the fuses? cheap and dirty fix would to replace the fuse.

After a new battery is tossed in, I'd try and disconnect the Polar FIS to see if that drain goes away.

Other than that are you making sure everything goes to sleep before checking for voltage drop across the fuses?
 

VW Derf

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Yup, I did the standard thing to flick the door switch and hood, armed the car and wait two hours to ensure everything was asleep.



For the voltage draws, they were 0.1 and 0.2 mV for the 5amp fuses and 0.6mV for the 15A fuse, no fuse pulling. The latter reading is my concern.


As for the battery, I think it may be toast due to the voltage drain down to 3volts as it is only 18 months old while the original lasted 7 years.


I did confirm that the PolarFIS was not shown on the MFA before arming the car, but to be sure, I'll remove it for my next test.
 

Vince Waldon

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Fuse 11 - 11 mA
Fuse 10 - 6 mA
Fuse 8 - 133 mA (0.6mV on a 15Amp fuse).
At a high level, any diesel automotive battery in good shape should able to supply small loads like that for weeks and weeks. :)
Assuming an 80 Ah battery, my back-of-the-envelope says the battery should deliver 150 mA for at least 22 days before dropping below starting threshold.

So, like KERMA, I'd not be concerned about those drains per se... anything south of 200mA overall seems to be the norm for a car with computers, modules, and the odd stereo. :)

That said, if the 150-ish mA above is draining your battery in a couple of weeks... and that's the only drains there are... yeah, probably time for a battery capacity test with a load tester. If that's the OEM battery and you got 8 years out of it... well done!

The 13.4V charging voltage does seem a little low...particularly if that was right at the battery posts, with a known accurate multimeter. If it was a really hot day that might explain it... the charging voltage is somewhat temperature-dependent.
 
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Ol'Rattler

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Put the battery on a charger overnight. If the charging Amps don't fall below 1 to 2 Amps (stays at say 4 Amps) the battery is shot. If you do a lot of short trips, the battery voltage can get low to which makes the charging voltage low which can make the battery not get a full charge from the alternator.

With fuse 8 out, you should be able to figure out what it powers.
 

VW Derf

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If you do a lot of short trips, the battery voltage can get low to which makes the charging voltage low which can make the battery not get a full charge from the alternator.
I'm beginning to think that that is a contributing factor and that my alternator may no longer be working at full capacity.

I've been watching the voltages change and for instance when the car is running and I turn the fan on to high voltage drops down to 12.8 or sometimes 12.6 (about 0.2v to 0.4v loss) depending how charged the battery is and it slowly returns. Watching the voltage when the car is running now is between 12.8 and 13.5, depending how long I drive. Generator load seems to run between 30% and 50% now and I haven't seen it go over 55%.

I'll get the batter charged again on a charger and see.
 

Vince Waldon

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I've been watching the voltages change and for instance when the car is running and I turn the fan on to high voltage drops down to 12.8 or sometimes 12.6 (about 0.2v to 0.4v loss) depending how charged the battery is and it slowly returns.
Yeah, on the surface those are not good numbers, but again it does depend a bit on where you are measuring that voltage.

If at the battery posts with a good DMM... not good.

If using the MFA or a Scangauge, which for whatever reason is downstream of a big load like the rad fans, and there's some extra resistance in that particular circuit.. possibly a red herring.

For example, my Scangauge can be 0.5 to 0.75 volts lower than the reading I get at the battery posts... depending on if the A/C has forced the rad fans on or if I have the cabin fan on. A nuance of how my car's OBD2 port is wired and the various resistances in my 12 year old car, I guess. :)
 

compu_85

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On our 99.5, I found the mystery battery drain was caused by the glove box light not turning off when the door was closed lightly.

-J
 

VW Derf

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Ya, from the VCDS there is about 0.1v-0.2v loss between the readings I provided and the battery terminals. Either-way I thinking I need to resolve what looks to be a charging issue first. I think the battery is fine now, but I haven't a chance to get it load tested yet.
 

JSWTDI09

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Y I think the battery is fine now, but I haven't a chance to get it load tested yet.

If you have a DVM (DMM) with a min/max function a quick and dirty load test is just to put the meter on the battery, set it to record the minimum, and start the engine (preferably cold). If the minimum voltage drops much below 10 volts the battery is suspect, below 9 it is probably bad.


Needless to say this is not as good as a complete load test, but it is free, if you have access to the right DVM.


Have Fun!


Don
 

VW Derf

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I got busy over the summer and never followed up too closely on this. That said the battery and alternator tested out fine. I'm pretty sure I've narrowed this down to the radio just not going fully to sleep. Pull the fuse for the radio (fuse 8) and everything was back to normal with no extra current draw.

During the debugging I even pulled out the Polar-FIS out and the extra draw was still there. Now that it is getting colder it is starting to drain the battery enough for rough starts if I leave the car long enough. :(

The radio does have one error code though (excluding the sat subscription code):
01303 - Telephone Transceiver (R36)
004 - No Signal/Communication
Freeze Frame:
Fault Status: 01100100
Fault Priority: 6
Fault Frequency: 1
Reset counter: 113
Now the polar-fis uses the telephone section of the MFI to do the readings but I don't have any sort of telephone interface or Bluetooth on the car. Could the two be related somehow? I have no idea, but could the radio keep searching for the telephone and not going to sleep or something?

I checked the CAN-Gateway controller and bit 5 is enabled for the telephone. If I turn it off, then the interface to the Polar-FIS is gone. That said I guess that would be another test to disable the telephone interface and see if the issue goes away.

Does anyone have other ideas?
 

Wilkins

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Without checking I think that is the same error code I have had ever since I installed the Polar FIS. I don’t have a problem with battery drain.
 

gmcjetpilot

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You have to let the car sit for 30-60 minutes (ore more). Unfortunately you
can't OPEN you car door to check fuses. Since fuses are in the side of the
dashboard only accessed with door open you are kind of screwed. Opening
door takes car out of sleep mode.

Soooo you have two ways....

One) Open driver door and use a screw drive to trip lock closed (don't forget
to open latch later when closing door). You need to clamp the door open
switch. Then wait for car to go into sleep mode. INSTEAD of removing fuses
use voltage drop across the fuses. There is a chart that will tell you current
for different fuses. You multi meter has to battery sensitive to micro volts.
Removing fuses may trip car from sleep mode.

Second) Put Amp-meter in series without out loosing connection between
battery and ground. It can be done. You clip one end of meter to the cable
terminal and another at ground. Remove battery terminal from battery. You
should NOT be seeing over 0.050 amps (50 milli-amps).
 

VW Derf

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You have to let the car sit for 30-60 minutes (ore more). Unfortunately you can't OPEN you car door to check fuses. Since fuses are in the side of the
dashboard only accessed with door open you are kind of screwed. Opening door takes car out of sleep mode.

Soooo you have two ways....

One) Open driver door and use a screw drive to trip lock closed (don't forget to open latch later when closing door). You need to clamp the door open switch. Then wait for car to go into sleep mode. INSTEAD of removing fuses use voltage drop across the fuses. There is a chart that will tell you current for different fuses. You multi meter has to battery sensitive to micro volts.
Removing fuses may trip car from sleep mode.

Second) Put Amp-meter in series without out loosing connection between battery and ground. It can be done. You clip one end of meter to the cable terminal and another at ground. Remove battery terminal from battery. You should NOT be seeing over 0.050 amps (50 milli-amps).
Thanks for the recap gmcjetpilot. I did it similar by arming the car with the doors and hood open (flipping the latch) and then did the tests about two hours later.

I didn't do the amp check, rather I measured the voltage drop in mA across the fuses and then referenced it against this chart: https://static1.squarespace.com/sta...79335/Fuse_Voltage_Drop_Chart_-_Mini_Fuse.pdf

From that I got the 0.6mV drop on the 15Amp radio fuse which equates to 133mA. Add the 17mA I found on the other circuits and I'm around 150mA, well outside of acceptable range.

I just pulled the fuse the other day on the radio to confirm my suspicions that the radio is the culprit and that seems to be the case as starting the next morning was fine. Unfortunately, I wasn't able to double check the voltage drop overnight. Either way I do have a draw and it really looks like the radio at this point. The question is why?

Without checking I think that is the same error code I have had ever since I installed the Polar FIS. I don’t have a problem with battery drain.
Wilkins, I noticed you also have a Canadian 2010 Golf wagon as well. Can I assume you are also without Bluetooth on the radio?
 

VW Derf

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Just a quick note to wrap up this thread with a solution. Turned out that my issue related to my RCD-510 radio never shutting off completely when the ignition was out or the car alarmed. I replaced it with a used eBay unit a while back and all is working well. I no longer need to put the fuse in if I wanted the radio for a longer drive. :)

Of course the draining killed the battery enough times, so that was replaced under warranty and under a load test the alternator is just above the acceptable level.
 
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